The structural and functional implications of reversible thermotropic membrane transitions, first discovered in this laboratory, will be further explored. The principal technique used will be differential scanning calorimetry, supplemented with such additional techniques as X-ray diffraction, circular dichroism and absorption spectroscopy, and nuclear magnetic resonance spectrometry. The major problems to be approached via calorimetry include the effects of membrane transitions upon growth, active transport, and passive leakage in cells; the role of counterions and glycolipids; the kinetics of transitions and the diffusion and de-mixing of lipids during the transition; the nature of association of lipids with biologically-active proteins; and the nature of the mixing of lipids in the membrane bilayer. In addition, the use of dilatometry as a tool in membrane and lipoprotein research will be explored. Experiments will be carried out with an extremely sensitive scanning dilatometer. Assigning the cause for the abnormally high coefficients of expansion, which appear to be unique to membranes and singly-walled bilayer vesicles, will be a major goal, to be accomplished by the combined approaches of dilatometry, heat capacity measurements, chemical modification, model systems, and deuteron resonance. The expansion of biological membranes with temperature is also unique in that the coefficients of expansion show a great deal of fine structure in the physiological temperature range. Hopefully, this phenomenon will also be explained. It is expected that the results will give new insight into both membrane structure and function on the molecular level.